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Java 17 LTS vs. Java 21: Key Features and Migration Guide

Compared with Java17, Java21 has significantly improved concurrency, language features and performance. It is recommended to migrate as soon as possible. 1. Virtual threads (formal) greatly reduce resource overhead in high concurrency scenarios and simplify asynchronous programming; 2. Structured concurrency (preview) improves the readability and reliability of multi-threaded code; 3. Pattern matching and recording patterns enhance conditional judgment and data deconstruction capabilities; 4. ZGC supports concurrent class unloading to reduce pause time; 5. Default UTF-8 encoding solves cross-platform garbled code problems; 6. External functions and memory APIs provide safer local calling methods; dependency compatibility (such as SpringBoot3), adjust JVM parameters, update build configuration, enable preview features and conduct full testing, especially

Jul 27, 2025 am 12:42 AM

java lts

The Complete Guide to the Java `Optional` Class

Optional is a container class introduced by Java 8 for more secure handling of potentially null values, with the core purpose of which is to explicitly "missing value" and reduce the risk of NullPointerException. 1. Create an empty instance using Optional.empty(), Optional.of(value) wraps non-null values, and Optional.ofNullable(value) safely wraps the value of null. 2. Avoid combining isPresent() and get() directly. You should give priority to using orElse() to provide default values. OrElseGet() implements delay calculation. This method is recommended when the default value is overhead.

Jul 27, 2025 am 12:22 AM

java optional

Debugging and Troubleshooting Common Java Application Issues

Checkstacktracesforexceptions,identifyingrootcauseslikenullpointersorclasspathissues.2.UseprofilingtoolslikeVisualVMandanalyzeheapdumpstodiagnosememoryleaksandhighCPUusage.3.InspectdependencytreeswithMavenorGradletoresolvemissingorconflictingJARsandv

Jul 26, 2025 am 08:04 AM

Implementing OAuth2 and OpenID Connect in a Java Application

OAuth2 is used for authorization, OpenIDConnect (OIDC) provides identity authentication based on OAuth2 to confirm user identity. 2. Using SpringBoot and SpringSecurity is the recommended way to implement OIDC in Java, and spring-boot-starter-oauth2-client dependency needs to be introduced. 3. Configure client-id, client-secret, scope (including openid, profile, email) and issuer-uri in application.yml to enable automatic metadata discovery. 4.

Jul 26, 2025 am 08:03 AM

Implementing the Saga Pattern in a Java Distributed System

Use the Saga mode to maintain data consistency in Java distributed systems, and replace distributed transactions through local transaction sequences and compensation mechanisms; 2. It is recommended to use orchestrated Saga in SpringBoot, and the OrderSaga class coordinates the execution and rollback of payment and inventory services; 3. Add retry, idempotence, and persistent Saga states to enhance reliability; 4. Linear process optimization orchestration is considered in complex event-driven scenarios.

Jul 26, 2025 am 07:56 AM

Comparing Java Web Servers: Tomcat vs Jetty vs Undertow

UseTomcatforenterpriseenvironmentsneedingbroadcompatibilityandtoolingsupport.2.ChooseJettyformodular,embeddableapplicationswithheavyasyncorWebSocketusage.3.OptforUndertowwhenhighperformance,lowlatency,andnon-blockingI/Oarecritical,especiallyinmodernm

Jul 26, 2025 am 07:51 AM

Java Reflection API: Power and Pitfalls

The core answer to reflection is: it is a double-edged sword that can realize dynamic operational structures at runtime, but it needs to be used with caution to avoid performance, safety and maintenance issues. 1. The power of reflection lies in dynamically creating objects, calling methods, accessing private members and extracting generic type information, which is widely used in frameworks such as Spring and Hibernate. 2. The main risks include high performance overhead, disruption of packaging, runtime errors caused by bypassing compile-time checks, and compatibility issues with new features such as Java module systems. 3. Suitable for use in framework development, plug-in systems, unit testing and generic type recovery, and should be avoided in ordinary business logic, performance-sensitive scenarios, or polymorphic substitutions. 4. Best practices include priority use of interface design and ease of

Jul 26, 2025 am 07:50 AM

Understanding Bytecode and the Java Compilation Process

Java programs do not run directly on the computer, but are first compiled into bytecode and then executed by the JVM; 1.javac compiles the .java file into platform-independent bytecode (.class file); 2. JVM's class loader loads the .class file; 3. Bytecode validator checks security; 4. JVM executes bytecode through the interpreter, and the JIT compiler dynamically compiles the hotspot code into local machine code to improve performance; this mechanism realizes Java's "write once, run everywhere", while ensuring security and execution efficiency. Finally, through tools such as Java, you can also view bytecode instructions, which fully demonstrates the entire process from Java source code to local execution.

Jul 26, 2025 am 07:49 AM

java Compilation principle

The Role of the `serialVersionUID` in Java Serialization

serialVersionUIDisaversioncontrolfieldinJavausedtoensurecompatibilitybetweenserializedanddeserializedobjects;2.Itmustbedeclaredasprivatestaticfinallongandischeckedduringdeserializationtoverifyclasscompatibility;3.Ifnotexplicitlydeclared,theJVMgenerat

Jul 26, 2025 am 07:48 AM

java serialization

Java Development with Visual Studio Code

It is completely possible to use VisualStudioCode for Java development, especially suitable for small and medium-sized projects, learning or hybrid multilingual development. 1. Install the ExtensionPackforJava plug-in, which includes syntax support, debugging, testing, Maven and project management functions; 2. Configure the JDK environment, it is recommended to use OpenJDK11 or 17, and set JAVA_HOME. VSCode can automatically recognize or manually specify paths in the settings; 3. Create a project by using Maven through the command line or use the "Java:CreateaJavaproject" command in VSCode to quickly generate standard structures; 4. Enjoy intelligent completion and reconstruction when writing code.

Jul 26, 2025 am 07:46 AM

java programming

Building Scalable Java Applications with Vert.x

Vert.x is a lightweight, high-performance JVM-based toolkit for building responsive, non-blocking applications suitable for high concurrency, real-time interactive scenarios. 1. It adopts non-blocking I/O and event loop models to improve throughput; 2. Supports multi-language development to facilitate team collaboration; 3. Provides modular design, which can use HTTP servers, WebSockets and other functions as needed; 4. Naturally supports microservice architecture, and realizes inter-service communication through EventBus; 5. It can be used in real-time data processing, API gateways, microservice underlying runtime and other scenarios; 6. Be careful to avoid blocking operations in event loops, and it is recommended that time-consuming tasks be handed over to the Worker thread pool for processing.

Jul 26, 2025 am 07:41 AM

Advanced Java Logging with SLF4J and Logback

SLF4J Logback has become the preferred solution for Java logging due to its flexibility, performance advantages and ecological support. 1. SLF4J is a log facade, allowing switching of underlying implementations without changing the code; 2. Logback is its native implementation, with better performance than Log4j and rich configuration; 3. SpringBoot and most open source libraries integrate this combination by default to avoid binding conflicts; 4. Support multi-environment logging policy through logback-spring.xml configuration file; 5. Use RollingFileAppender to implement log archiving and automatic cleaning; 6. AsyncAppender improves log writing performance; 7. Reasonably set the log level (TRACE/DEBU

Jul 26, 2025 am 07:39 AM

slf4j java log

The Internals of the Java `final` Keyword

ThefinalkeywordinJavaenforcesimmutabilityatcompiletimeandenablesruntimeoptimizationsbyrestrictingreassignmentofvariables,methods,andclasses;2.Forfinalfields,theJavaMemoryModelguaranteessafepublicationwithoutsynchronization,ensuringotherthreadsseecorr

Jul 26, 2025 am 07:37 AM

How to Troubleshoot and Fix Memory Leaks in a Java Application

Identify signs of memory leaks, such as continuous growth in memory usage, frequent complete garbage collection, OutOfMemoryError exceptions and slow application; 2. Use jmap or JVM parameters to generate heap dump files, and use tools such as EclipseMAT and VisualVM to analyze them, focusing on the "LeakSuspects" report; 3. Common reasons include unlimited growth of static collections, unclosed resources, unlogged listeners, internal class hold external class references, and class loader leakage. Weak references, try-with-resources, timely unbinding, static internal classes and cleaning up ThreadLocal should be repaired respectively; 4. Through production environment monitoring, regular stress testing, code review

Jul 26, 2025 am 07:28 AM

java memory leak